The present invention relates generally to a medical device and more particularly to an apparatus for intra-operative examination of tissue and identification of target cells in-vivo.
During surgical operations to remove cancerous tumors, one of the greatest areas of uncertainty lies in determining whether all of the cancerous cells at the periphery of a tumor have been removed. Current standards of care call for the removal of all cancerous tissue by removing a surrounding layer of healthy tissue. That is, current standards of care call for the resection of more tissue than believed necessary to remove the cancer. This “extra” layer of healthy tissue is referred to as a “healthy margin” and can range from a single cell to 10 mm or more in depth.
After the tumor with its margin has been removed, the tissue is sent post-operatively to a pathologist for in-vitro examination of the margin. The pathologist examines multiple representative points along the margin to assess whether cancerous cells exist at the edge of the excised tissue. That is, the pathologist attempts to determine whether the margin contains cancerous cells. Thus, the pathologist conducts a cellular-level review of the excised tissue to determine if the tissue within the margin includes cancer cells. If cancer cells are found at or close to the surface of the specimen, re-excision is often recommended and the patient must undergo a second surgical procedure when possible.
Even where the pathologist determines that the margin is clean, patients may still undergo forms of post-surgical therapy to the tumor bed due to the fact that the in-vitro analysis of the tissue cannot definitively determine if all cancer cells surrounding the cancer were removed. For example, it is not uncommon for the margin to be damaged, such as by staples or other devices used during the resection. In these cases, it may be difficult to properly analyze the margin. As such, the standard of care often dictates that the patient receive post-surgical therapy, such as radiological therapy, which has a high cost and, in and of itself, has detrimental health effects. It is estimated that at least two-thirds of all cancer patients have all cancer cells removed during an operation, yet most cancer patients receive radiation therapy post-operation. Many of these patients may be spared this treatment if it was more definitively known whether all of the cancerous cells were removed during surgery.
Thus, in-vitro pathological analysis has a number of advantages and disadvantages. Advantageously, in-vitro pathological analysis allows for a careful, cellular-level analysis of tissue in a controlled environment. Unfortunately, to provide these advantages, “extra” tissue must be removed and, because this analysis is of cells removed from the body instead of the cells remaining in the body, at best, the analysis provides an indication of what may be present in the body. That is, the in-vitro analysis cannot provide a definitive answer of whether all cancer cells were removed and, often, subsequent surgeries and/or radiation therapy is dictated by the standard of care.
As such, extensive research has been directed towards methods of reducing the uncertainty in tumor removal through in-vivo examination of the removal site or the excised tissue. As will be described, a variety of systems and methods have been developed to analyze tissue in vivo; however, as will be described, each is plagued by its own set of disadvantages.
Some in-vivo examination systems use optically-based molecular probes. These optical probes emit light when interacting with a target cell. Such probes can be fluorophores, luciferase, fluorescence resonance energy transfer (FRET) between chromophores, quantum dots, or dyes. To reach the single-cell analysis level, much like the in-vitro process described above, a form of microscopy or optical magnification is employed. While exhibiting a high degree of sensitivity, such detectors are difficult to use in-vivo. In order to detect single cells on the order of, for example, 20 microns, both the field of view (FOV) and depth of field of these detectors are typically constrained to tens of microns. These technologies, therefore, are not suited for scanning for a small number of cells over a relatively large area, such as a centimeter. For example, some in-vivo optical probe visualization systems have used a fiber-optic-coupled confocal microscope, such as the Cellvizio system. Cellvizio is a registered trademark of Mauna Kea Technologies of France. While able to achieve single-cell resolution during an in-vivo examination, the FOV of such microscopes is limited to 0.2 mm. Others have attempted to use an optical catheter with a 460 micron FOV and pneumatically adjustable focal point with a nominal 26 micron focal distance adjustable mechanically up to 200 microns. However, this device is similarly limited by its small FOV.
While microscopes having greater focal planes can be employed, the depth of field is still narrow and the microscopes require that a fixed distance is maintained between the lens and the cells of interest. Thus, these systems, generally, are not feasible for a definitive analysis of tissue in-vivo due to natural motions, such as blood flow, small muscle movement, breathing, and the like. That is, unlike the controlled environment of a pathology laboratory, microscope-based analysis tools are generally found to be unsuitable for use in-vivo to analyze the results of surgical procedures due to the natural interference with cellular analysis presented by fluids, motion, and the like. Hence, at best, such systems can be used to attempt to gain some in-vivo information, but in-vitro analysis of a margin is still required.
Beyond optical imaging, other detection techniques include nuclear magnetic resonance (NMR) with magnetic nano-particle probes and in-cell NMR with isotopes of nitrogen and carbon. However, the sensitivity of nano-particle NMR techniques is on the order of millimeters and, therefore, this technology can not detect at the single-cell level. While in-cell isotope tagged NMR is more sensitive, the resolution is still only several hundred cells in-vitro. Thus, like microscope- or magnification-based, in-vivo analysis tools, such systems are only suitable for attempting to gain some in-vivo information, but in-vitro analysis of a margin is still required.
Some have attempted to use other analytical mechanisms than optical analysis or NMR analysis. For example, some have attempted to use the electrical and/or electro-magnetic properties of cells to determine a given cell is cancerous. In these systems, a probe is used to analyze the patient's tissue following resection. Advantageously, these systems allow for in-vivo analysis of a sufficiently large analysis area and can be properly utilized in the presence of fluids, motion, and the like. Unfortunately, they do not provide for individual, cellular analysis and have varying and/or limited analytical depths. Also, unlike optical- or NMR-based systems that allow for direct, cellular analysis, these probes rely on an indirect analysis of cells through the electrical properties of the cell. Thus, they do not provide for sufficiently definitive analysis to conclude that all cancer cells have been removed.
Therefore, it would be desirable to have a system and method for in-vivo analysis of tissue that is capable of analyzing a substantially large volume of tissue with sufficient accuracy to provide clinical certainty of tissue pathology.